The present invention relates to an electrophotographic recording material made of an electrically conductive support and at least one binder-containing photoconductive layer which contains a perylenetetracarboxylic acid derivative, as a compound which produces charge carriers, and a hydrazone or pyrazoline derivative, as a compound which transports charges.
It is known (German Offenlegungsschrift No. 2,919,791, corresponding to U.S. Pat. No. 4,278,747) to use electrophotographic recording materials which contain, in the organic photoconductor layer, a very wide variety of hydrazone compounds having an aromatic hydrocarbyl group or an aromatic heterocyclic group. The photoconductor layer can additionally contain dyestuffs and/or electron acceptors which form a charge transfer complex with the hydrazone compound. It can also be combined with such materials as selenium, selenium compounds, cadmium sulfide, phthalocyanine pigment, perinone or perylene pigment, or bisazo and cyanine pigment.
It is also known (U.S. Pat. No. 4,030,923, corresponding to German Offenlegungsschrift No. 2,654,873) to use an electrophotographic recording material in which a photoconductor layer contains triarylpyrazoline in conjunction with binder mixtures as a charge transport layer. Highly abrasion-resistant materials are obtained when polycarbonates combined with bisazo pigments are used as binders.
It is further known (German Pat. No. 2,924,865, corresponding to U.S. Pat. No. 4,278,746) to use, in electrophotographic recording materials with a conductive support, binder-containing charge transport layers incorporating pyrazoline compounds which can be combined with a very wide variety of substances producing charge carriers and with polymeric binders. It is also known (U.S. Pat. No. 3,904,407, and German Offenlegungsschrift No. 2,237,539, corresponding to U.S. Pat. No. 3,871,882) to use, in photoconductive systems, perylene pigments, in particular perylenetetracarboxylic acid derivatives, as compounds which produce charge carriers. Perylene pigments are also known from U.S. Pat. No. 3,972,717. German Offenlegungsschrift No. 3,019,326 reveals the use of a certain crystal modification of the N,N'-bis-(3-methoxypropyl)-diimide of perylenetetracarboxylic acid.
The known recording materials are highly light-sensitive, particularly in a photoconductor double-layer arrangement of a layer producing charge carriers and a charge transport layer. Their mechanical resistance properties are additionally promoted by using compatible high-polymeric binders. For instance, vacuum-deposited layers of perylenetetracarboxylic acid derivatives can be combined with charge transport layers which contain polyester or cellulose-ester binders. These recording materials, although highly light-sensitive, are somewhat brittle, leading to fine hairline cracks in the layers, or they are not sufficiently abrasion-resistant. If, however, impact-resistant, highly abrasion-resistant polycarbonates or polyepoxides are incorporated in corresponding recording materials, either the good photoconductivity of the latter decreases or there evidently are incompatibility phenomena which disqualify the recording material from practical use in cyclic copying processes.
It is true that the known state of the art makes it possible, all in all, to obtain highly light-sensitive electrophotographic recording materials that are sensitive to relatively long wavelengths. Nevertheless, this sensitivity to relatively long wavelengths, as, for example, in the case of bisazo pigments, has to be filtered out again for office copiers in order to obtain practically correct color reproduction of the originals. It is regarded as a further disadvantage that photoconductor layers of this type can only be prepared in a double-layer arrangement when the layer containing the compound which produces the charge carriers is in a dispersion with a binder, since bisazo pigments will decompose if applied at elevated temperatures.